Pavement.



No. 797,408. PATENTED AUG. 15, 1905. G. W. (K; W. T. S. CRIGHPIELD.PAVEMENT.

APPLICATION FILED DEC. 20. 1904.

WITNESSES. INVENTORS AUORI/E C'TATES PATENT OFFICE.

GEORGE W. URIUHFIELD, OF JERSEY OlTY, NEW JERSEY, AND \VILLIAM T. S.CltliUHFlELD, OF NEW YORK, N. Y; SAID GEORGE W. lRlCHFlEliD ASSIGNOR TOSAID WILLIAM T. S. ORlOHFlELD.

WAVEMENT.

Specification of Letters Patent.

Patented Aug. 15, 1905.

Application filed December 20, 1904.. Serial No. 237,669.

./'0 all whom it may concern:

Be it known that we, GEORGE W. CRICH- FIELD, a resident of Jersey City,in the county of Hudson and State of New Jersey, and VII.- LIAM T. S.Ciuc'nirmnn, a resident of the city of New York, borough of Manhattan,in the county of New York and State of New York, citizens of the UnitedStates, have invented a new and Improved Pavement, of which thefollowing is a full, clear, and exact description.

The invention has for its object to provide an improved sheet orso-called monolithic pavement; and it relates to that general class inwhich the pavement is formed of bituminous or asphaltic mixtures.

Sheet-asphalt pavements as usually constructed are formed of a base orbinder laid. in a continuous sheet and having above it a wearing-surfaceformed of a mixture having greater elasticity than the base or hinder.Such pavements involve a great number of difficulties and disadvantages.Among these may be stated the fact that the material of which thesesheet asphalt pavements are formed must be laid hot, and great expenseand inconvenience are involved in transporting the hot material to thepoint at which the pavement is to be formed, and also injury is done tothe material from overheating; the pavement cannot be properly laid inextremely cold or stormy weather; a large body of skilled labor isrequired to lay the pavement, and a relatively slight fault on the partof any one may easily result in seriousinjury to the pavement; it isimpossible to effect a true or thorough connection between the base orbinder and the wearing-surface, resulting in the creeping of thewearing-surface and in consequent Lmevenness of the pavement, andrepairs can he made in the pavement only at serious inconvenience bothto traliic and to the operator. These difficulties render it almostimpossible for smaller cities, towns, and villagcs to employ the asphaltpavement as ordinarily laid. in overcoming these and other disadvantagesof the common practice we pro vide a pavement formed of a number ofseparate blocks of convenient size and of a peculiar composition, to behereinafter set forth. Each ofthese blocks comprises abase or bind er offirm rigid composition and a Wearing-surface of a high degree ofelasticity thoroughly and inseparably joined to the base, so as to formof the two layers a solid single block. These blocks are laid togetheron a suitable bed, and they are in a peculiar manner, to be hereinafterexplained, so effectually bound together as to form a continuous,unbroken, and practically monolithic or sheet pavement.

Reference is to be had to the accompanying drawing, illustrating apavement embodying the features of our invention, which drawingrepresents a sectional view of the pavement.

in said drawing, A indicates a bed on which the pavement is laid; B, theblocks, each comprising a base 6 and wearing-surfaces Z2 inseparablyjoined together, and C indicates the bond between the blocks, firmlyconnecting them and forming said blocks into a truly continuous ormonolithic paved surface.

The bed A may be of any material desired; but it is preferably concreteor other equivalent material, which will furnish a rigid substructure orsupport for the paving. The blocks B may be of various sizes. Forordinary work the dimensions twelve inches by five inches to twelveinches by three to four inches are preferable.

The base or hinder of the paving-block is of such composition as to giveit a high degree of rigidity, strength, and weight. It is composed of agranular mineral aggregation or mixture and a bitumen. It is necessaryto form the base or hinder as nearly solid as possible, so as to attainrigidity and strength. Looking to this end, therefore, we prefer to formthe base 5 of the block B of the following substances and in thefollowing manner: Trap rock, granite, or other hard stone is crushedinto particles from tln'ee-quarters of an inch or one inch in diameterdown through. all grades and sizes to an impalpable powder. This rockforms the base of the composition, and the purpose in crushing .itthrough all grades and sizes from three-quarters of an inch or one inchlumps to an impalpable powder is to enable the mass to be solidly packedtogether, the liner particles filling the interstices between the largerparticles, thus giving great weight and solidity for bulk. if desired torender the mixture of still greater density, filling all voids betweenthe particles, sand of various degrees of fineness, carbonate of lime,and Portland cement may oe, all or severally, added to the mixture, thusforming a mineral aggregate which may be packed with almost absolutedensity and which will furnish the required strength and rigidity. Thisaggregate is mixed in an ordinary asphalt-mixing machine, or in anyother suitable way, with a quantity of pure bitumen, which is preferablynine per cent. of the aggregate. To effect this mixture, the aggregateshould be first heated to about 250 Fahrenheit, and the asphaltic cementor bitumen, tempered with a fiux according to the desired practice,should be mixed with the aggregate at a temperature preferably notexceeding 300 Fahrenheit. The composition therefore formed of theabove-described mineral aggregate and the asphaltic cement or bitumenbrought together by heat is allowed to set or harden to form thefinished product under certain peculiar conditions, however, which willhereinafter fully appear.

The wearing-surface or top layer of the paving-block is formed with apeculiar composition which insures elasticity and toughness. This ispreferably a properly balanced or proportioned mixture of coarse andfine sand free from loam, salt, quicksand, silt, organic matter, orother substance deleteriously affected by the elements and notcontaining a marked excess of lime. The sand should be hard and shouldbe of such a degree of fineness that all of it will pass a ten-meshscreen, (figuring meshes per inch,) about five to eight per cent. shouldpass a twenty-mesh screen, twenty to thirty-five per cent. should pass afifty-mesh screen, ten to twenty per cent. a one-hundred-mesh screen,and at least a small percentage should pass a two-hundredmesh screen. Inthis manner a dense compact body is assured, since the finer particlesfill in the interstices between the larger particles. If desired, inorder to increase the density or compactness of this mass, ten per cent.to fifteen per cent. of an impalpable mineral dust may be added-forinstance, carbonate of lime, marble-dust, or sand-and to still furtherincrease the density two per cent. or three per cent. of Portland cementpassing a four-thousand-mesh screen may be added to the aggregate,increasing its compactness without increasing its bulk. The mineralaggregate thus carefully graded should then be incorporated with anasphaltic cement. This cement should be selected with great care. Weprefer to use none but a pure natural lake asphalt free from solublesalt, free sulfur, organic matter, glance-pitch, ironpitch, silt, loam,or other impurities, this asphalt being softened by a flux of puremaltha or liquid asphalt, showing a test of 9 to 15 Baume. The asphalticcement composed of these elements thoroughly incorporated the one withinthe other in such proportions as their respective natural consistenciesmay demand is then mixed with the mineral aggregate previously describedat a temperature of from 250 to 300 Fahrenheit. This composition formingthe elastic wearing-surface of the pavement preferably contains fromeleven to thirteen per cent. of pure bitumen, the amount dependingsomewhat upon the nature of the asphalt used as the base and itssensitiveness to heat. The nature of the composition of which thewearing-surface is formed enables us to employ nearly twice as muchbitumen as that which is contained in ordinary or commonly-used asphaltblocks, thus adding to that extent to the strength, elasticity, anddurability of the pavement.

The two compositions respectively forming the base and wearing-surfaceof the pavement being now mixed and heated, as described, should beseparately conveyed to their respective molds, which molds are of thesize and form similar to that of the paving-block to be formed. Thesemolds should then be superimposed, so that the two compositions yet inplastic form he together one above the other. The compositions shouldnow be subjected to extreme pressure tending to force the two layerstogether, and notwithstanding the differences in the materials of whichthe two compositions are formed the asphaltic cement embodied in eachwill cause the two compositions when forced together to adhere firmlyand inseparably,forming a solid block, the only division in which beingthat afforded to the eye by reason of the different materials with whichthe two compositions are formed. After sufficient pressure has beenapplied and the mass hardened sufiicientl y the finished pavingblockshould be removed from the molds. This block combines, therefore, in oneinseparable mass a semirigid base or binder and a tough elastic wearingor top surface. It is here pertinent to observe that the union thusefiected between the base and the wearingsurface of the paving-block isabsolutely perfect, and consequently far superior to that which iseffected between the two layers in an ordinary asphaltic pavement, andthe blocks may be transported indefinite distances much the same asgranite blocks, brick, wooden blocks, or the like.

In laying the blocks to form the finished pavement a suitable bed shouldbe provided, as indicated in the drawing, and the blocks are laid on thesame in any desired arrangement, the base 6 of the block bearing on thebed A and the wearing-surface b uppermost. After the blocks have beenlaid the joints between them are filled and the blocks thoroughly weldedor joined together by a mixture of hot asphaltic cement and Portlandcement in proportions of about forty parts of asphaltic cement to sixtyparts of Portland cement. This hot mixture poured into the joints iscaused to adhere or weld itself to the pavingblocks, particularly thewearing layers 6 thereof, by passing a hot instrument over the joints.

rezaee it i This instrument is preferably the ordinary hotsmoothing-iron employed in laying asphalt pavements. The result is theproduction of a pavement of perfect composition, the upper and lowerlayers, or, in other words, the wearing-surfaee and base, of which areinseparably joined and the upper surface of which is continuous andunbroken, forming a true sheet or monolithic pavement. The elasticwearingsurface of this pavement absorbs the concussion of traffic anddistributes the same first to the semirigid base or binder and throughthis to the concrete bed on which the pavementis laid. In this mannerthe weight and jar of the traffic are absorbed and distributed upon thesolid bed A, which is of such formation as to safely bear the loadimposed.

Having thus described the preferred manner of carrying out ourinvention, what we claim as new, and desire to secure by Letters Patent,is the following:

1. A pavement formed of separate compact blocks of granular mineralmaterial and a bituminous material laid together edge to edge andhomogeneously joined to each other by a bond formed of bitumen and apulverulent mineral whereby the bond is given essentially the hardnessand consistency oil. the blocks and a continuous sheet or monolithicpavement produced.

2. A pavement formed of separate compact blocks of granular mineralmaterial and bituminous material laid together edge to edge andhomogeneously joined by a bond containing bitumen and Portland cement,whereby to produce a continuous sheet or monolithic surface.

3. Apavementformed of separate, compact blocks, each made up of twolayers or strata permanently joined and of such variation in compositionas to make the upper stratum or wearing-surface elastic relatively tothe lower stratum or base, said blocks being laid together edge to edgeand homogeneously joined by a bond containing material contained in theblocks, whereby to form a continuous sheet or monolithic pavement with arelatively rigid base and a relatively elastic wearingsurface.

at. A pavement formed of separate compact blocks, each made up of twolayers or strata, permanently joined together and composed of granularmineral material and bituminous material of such form and quality as tomake the upper stratum or wearing-surface elastic relatively to thelower stratum or base, said blocks being laid together edge to edge andhomogeneously joined by a bond containing bitumen, whereby to produce acontinuous sheet or true monolithic pavement with a relatively rigidbase and a relatively elastic wearing-surface.

5. A pavement formed of separate compact blocks laid together edge toedge, each block being composed of a relatively elastic top or wearinglayer and a relatively rigid bottom or base layer and said blocks beingwelded together by a bonding material having an affinity to the materialor materials of which the blocks are formed whereby to produce a true orperfect bond between the blocks and a continuous sheet or monolithicpavement with an elastic wearing-Snriface and rigid base.

6. A paving-block tli'ori'ned of two layers or strata permanently orinse 'iarably joined together by pressure when in hot plastic condition,each stratum containing granular mineral material and bituminousmaterial and the composition of the layers being varied sufficiently tomake the top or bottom layer relatively elastic and the bottom or baselayer relatively rigid.

7 A paving-block formed of two strata or layers permanently orinseparably joined together by pressure when in hot plastic condition,each stratum containing granular mineral material of varying degrees oflineness and bituminous material and the composition of the layers beingvaried sufliciently to make the top or wearing layer relatively elasticand the bottom or base layer relatively rigid.

Iln testimony whereof we have signed our names to this specification inthe presence of two subscribing witnesses.

GEORGE W. CRICHF .ELD. l VlLLlAh l 71.. URIL {Fl ELI).

/Vitncsses:

lSAAO B. (imam, Jfuo. M. hirrreu.

